LIFETIME ENHANCEMENT OF ULTRASMALL FLUORESCENT LIQUID POLYMERIC FILM BASED OPTODES BY DIFFUSION-INDUCED SELF-RECOVERY AFTER PHOTOBLEACHING

The major concern with optodes, especially miniaturized ones, has been their photobleaching limited lifetime, Liquid polymer [highly plastic ized poly(vinyl chloride)] films are commonly used to prepare fluoresc ent optical fiber sensors. A major advantage is the ease of their fabr ication. It is demonstrated here that, with proper choice of excitatio n power and illumination time, the sensor will completely recover itse lf from photobleaching after each measurement. This self-recovery is d emonstrated on single-mode optical fibers with 80 mu m diameter (3.1 m u m active region) and on near-field scanning optical microscope pulle d fiber tips with submicrometer diameter (250 mn active region). The s ingle-mode optode can be used for 30 000 measurements with only a 5% s ignal loss at a signal/noise of >66. This opens the way for prolonged ratiometric application of such optodes.